It may be desirable to install modules (e.g., chip-carrying circuit cards, printed wiring boards, or the like) in a card rack for a cryogenic application, such as a superconducting supercomputer. In this use application, it may be desirable both to accommodate large modules and to provide uniform clamping force between the cards and the rack. The card rack should maintain clamping force at cryogenic temperatures (e.g., less than or equal to about 123K), and low thermal resistance between the rack and the card(s) carried thereby is required. Desired thermal performance can be achieved by uniform contact pressure between the cards and the card rack.
The current state of the art approach to module/card rack installation includes the use of wedgelocks. These have been used in currently known assemblies. The limitation of the wedgelock approach is that both the card rack and module/card must of the same material in order to achieve desired thermal conductivity in the use environment. In addition, the wedgelock system requires multiple very small shims or wedges, adding complexity to assembly of the system. Wedgelocks are also extremely expensive, with multiple wedgelocks needed for a particular instance of a card rack system. There is also a risk of adverse effects to the system if a wedgelock malfunctions (e.g., does not clamp as intended) or is located out of position (e.g., falls loose and interferes with electrical connections in the system). Finally, because wedgelocks are present at discrete sites along the card slots, there are local high/low clamping force areas along the length of the card slot, as well as relatively low thermal transfer between the modules and the card rack because of the noncontiguous placement of the wedgelocks along the card slot.